System for transmitting electroradiant energy



Feb. 28, 1933. 5 pURlNGTON 1,899,527

SYSTEM FOR TRANSMITTING ELEGTRORADIANT ENERGY Filed Dec. 25, 1925 INVENTOR ON 5. PUPJNGTON ATTORNEY Patented Feb. 28, 1933 arrae EN? @FFE ELLISQN S. PURINGTON, OF GLOUCESTER, MASSACHUSETTS, ASSIGNOR TO JOHN HAYS HATLIIEOND, .13., OF GLOUCESTER, IIIASSAGHU'SETTSv SYSTEM FOR TRANSMITTING ELEGTRORADIANT ENERGY Application filed December 23, 1925.

This invention relates to radio transmission systems and particularly to an improved system for more efiicient transmission of radio signals.

' The purpose of this invention is to provide an 'eficient transmission system for wireless signalling by coupling together in a new and improved manner two or more vacuum tubes,

one or more of which may be caused to produce oscillations.

An object of this invention is to provide a simple arrangement for effecting the, modulation of an oscillating system.

Another object of the invention is to prevent losses in a modulating audion tube emcillator.

Another object of this invention is to provide a suitable circuit for by-passing any high frequency currents to keep them from the modulator tube.

Another object of the invention is to provide means for obtaining proper feed back voltage for the grid of a space discharge device independcnt of tee frequency and constants of the oscillatory circuit over a considerable range.

Another object of this invention is to couple two oscillating circuits together in such a way that the frequency of one may be changed without affecting the other.

Another object of this invention is to provide means whereby one of the oscillators may be of the mechanical type.

Still another object of the invention is the construction of an oscillation circuit employing a mechanical oscillator in which all that need be done to change the frequency generated is to replace the mechanical oscillator with one of the proper frequency characteristics.

Still another object is to apply a radio oscil- Serial No. 77,194.

lating device as a driverfor a mechanical oscillator.

Further objects will appear from consideration of the specification and drawing the latter of which The single figure is a schematic diagram of the connections involved in an embodiment of the present invention.

The embodiment of this invention illustrated in the drawing shows a low frequency or modulating oscillator 1 and a high frequency or radio oscillator 12 connected by circuits so that the high frequency oscillations produced by the radio oscillator are modulated by the low frequency oscillations.

The oscillating'modulator triode 1 has connected across its anode and cathode through a condenser 4 on the anode side an oscillatory circuit 23. The oscillating circuit may be keyed by means of a key 5 connected in circuit with a condenser 6. The frequency of oscillations produced by tube 1 is determined chiefly by the oscillatory circuit 2, 3 and the keying condenser 6. Consequently the frequency of oscillation is altered by closure of the key and by this alteration signalling is of fected. Instead of the keying being done by changing the capacitance of the oscillatory circuit, it may be adapted to vary the inductance of the oscillatory circuit. The oscillatory circuit is connected to the cathode 7 in the usual manner.

The platev current is supplied by a direct current generator 8 through an inductive impedance or choker coil 9. The generator is shunted by a condenser 10 which will allow by-passing of any alternating currents which may leak through the choke coil 9.

Grid excitation is obtained by coupling in a proper manner an inductance 11 connected between the grid and cathode of tube 1 to the inductance 2 of the oscillatory circuit 2-3.

A grid leak is employed as shown in a well-known manner.

The radio oscillator of the system consists of a vacuum tube 12, the plate and filament of which are connected to the direct current source 8 substantially in parallel with the plate and filament of the tube 1. The radio oscillator includes an oscillatory circuit which consists of an inductance 13 to which is variably connected the plate of the tube 12 through a condenser 14:. The antenna 16 is also tapped variably to inductance 13 through a condenser 15, and the capacity to the ground indicated by 17 completes the oscillatory circuit.

The oscillatory circuit 23 of the moduiating oscillator is connected to the anode and cathode terminals of the radio oscillator 12, thereby placing the two tubes in parallel relation. Connections to the anode of the tube 12 are made through condenser 14 and inductance 18.

Thecircuit 4#36 is so constructed as to provide a capacitance path which will bypass any radio frequency currents produced by the tube 12 and thus prevent them from being impressed across the modulating os cillator 1. By so doing, losses in the modulating tube are very effectively prevented. Also with the above mentioned bypassing circuit, the inductance 18 need be of only small value numerically, which, as can be readily understood, is very desirable.

If the grid 19 of the tube lwere separately excited, as is done in many instances, it would not be possible to by-pass all of the high frequency currents, as a condenser large enough for this purpose could not be used Without imposing a considerable capacitance load on the modulator, thereby impairing its efficiency.

As shown, grid excitation and feed-back for the radio oscillator tube 12 is obtained by coupling the grid to the antenna inductance 13 through a transformer, the primary of which is in parallel relation to inductance 13. The correct adjustment of the feed-back is dependent only upon the frequency at which the oscillatory circuit is to operate, so that in adjusting the transmitter to an antenna of unknown constants, the plate and wave length taps only need to be varied to produce the correct adjustment. The usual grid leak is also employed in connection with this tube.

If secrecy is desired'in the transmission and reception of signals by this system, the low frequency must be of an inaudible frequency and the high frequency oscillations may be wobbled in frequency as by cyclically inserting condenser 20 in the oscillatory circuit in conjunction with lzeying the low frequency oscillations, making it imperative to use a double detector system to receive the signals. A. receiver suitable for receiving under these conditions is shown in patent to Hammond No. 1,540,881 of June 9, 1925. Attention is also directed to patent to Chafiee ct al No. 1,690,719 the general nature of the signal of which is the same as in the present application excepting that ordinary plate modulation is used.

In the operation of the present system both tubes are set to oscillating, the radio oscillatory tube at a high frequency and the modulating oscillator tube at a low frequency which latter frequency will vary the ampli tude of the oscillations of the hi h frequency Waves. Thelreying of the modulating oscillatory circuit changes the frequency of modulation for signalling purposes.

The invention is not limited to the above uses which are described merely as illustrations, but on the other hand, may be utilized in many ways as will be defined in the appended claims.

I claim:

1. In a radio system, a three electrode vacuum tube, an oscillatory circuit energizedby said tube, a grid circuit for said tube coupled for feed-back to said oscillatory circuit, a second vacuum tube associated therewith, a capacitance path between the circuits connecting the plates and filaments of said tubes, an oscillatory circuit for said second tube, an inductive circuit coupled in parallel with said second oscillatory circuit and a grid filament circuit coupled to said inductance circuit to produce feedback to the grid of said second tube. i

2. In a radio system, an osillating modulator audion tube, an oscillatory circuit for said tube, a grid circuit coupled to said oscillatory circuit to produce grid excitation, a radio oscillatingtube associated therewith, circuits connecting the plates and filaments of said tubes in parallel, a capacitancecircuit between said connecting circuits, an oscillatory circuit for said radio oscillating tube, astoppage condenser connected to said circuit, a second circuit in parallel relation withsaid oscillating circuit and in series with said condenser, a grid circuit coupled by transformer coupling to said second parallel circuit to provide feed-back currents to said grid and an antenna for radiating signals produced by said system.

3. In a radio system, a vacuum tube oscillator for generating high frequency oscillations in an oscillatory circuit, a second associated vacuum tube for generating low frequency oscillations in an oscillatory circuit constructed to modulate the amplitude of the high frequency oscillations, a grid circuit for the low frequency oscillator coupled to the low frequency oscillatory circuit, a grid circuit for the high frequency oscillator coupled in parallel through a transformer circuit to the high frequency oscillatory circuit, means for causing changes in the frequency of the low frequency oscillations, means for wobbling the frequency of the high frequency oscillations and a capacitance circuit between the two tubes for by-passing high frequency currents.

4. In a modulator system, a circuit includmodulated, a circuit including a source of modulating energy, said last named circuit comprising an electron discharge device having an anode, a cathode and at least one grid electrode, a circuit including a coupling device connected between said grid electrode and said cathode, a low impedance path for high frequency currents, including means capable of determining the frequency of the modulating energy, connected between said anode and cathode and means for coupling said low impedance path to said coupling device, means for connecting said first named circuit in parallel with said low impedance path whereby the high frequency energy is in effect localized in said first named circuit and thereby substantially prevented from being communicated to said second named circuit.

5. In a modulator system, a source of modulating energy comprising an electron discharge device having an anode, a cathode and at least one grid electrode, a circuit including a source of current and alternating current stopper means connected between said anode and cathode, a circuit including a coupling device connected between a grid electrode and said cathode, and a circuit including means for determining the frequency of oscillations produced by said source connected between said anode and cathode and adapted to be coupled to said coupling device, said last named circuit having the said means thereof arranged so as to form a low impedance path for high frequency currents, and a source of high frequency current connected across said anode and cathode in parallel with said last named circuit.

6. In a modulator system, a source of high frequency energy to be modulated, a source of modulating energy said last named source comprising an electron discharge device having an anode, a cathode and at least one grid electrode, a circuit including a source of current connected between said anode and cathode, a second circuit including a coupling device connected between a grid electrode and said cathode and a third circuit forming a low impedance path for high frequency currents including means for determining the frequency of the modulating energy connected between said anode and cathode, means for coupling said third circuit to said coupling device, and means for connecting said source of high frequency energy in parallel with said last named circuit.

7. In a signalling system, a carrier frequency circuit including a space discharge device having input and output circuits, the output circuit being tuned to the carrier frequency, a low impedance path for the carrier frequency and carrier frequency impeding means both thereof forming a series arrangement connected in parallel with the output circuit, a source of space current for said discharge device shunted across the low imped device.

ELLISON S. PURINGTON. 

